The Experts below are selected from a list of 9531 Experts worldwide ranked by ideXlab platform
Qiang Huan - One of the best experts on this subject based on the ideXlab platform.
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a high sensitivity and long distance structural health monitoring system based on bidirectional SH Wave phased array
Ultrasonics, 2020Co-Authors: Qiang Huan, Mingtong ChenAbstract:Abstract When estimating a structural health monitoring (SHM) system, its defect sensitivity and area/distance coverage are most important factors. For commonly used guided Wave sparse array system, it usually requires a reference state as the baseline which is not available in many cases. In comparison, phased array technique typically does not need the baseline in simple structures and it had been successfully used in nondestructive testing (NDT). However, currently developed phased array systems employed omni-directional transducers routinely, where the Wave energy is distributed equally along all directions thus it is not favorable for long-distance detection. In this work, bidirectional piezoelectric transducers were used to form a linear phased array system, which can generate/receive SHear horizontal (SH) Wave with high energy concentration. Firstly, the configuration of the employed transducer composed by antiparallel d15 piezoelectric strips (APS) was presented. Then the total focusing method (TFM) employed for defect detection was introduced. After validating the radiation pattern of SH Wave generated by the APS, the properties of beam steering for the proposed phased array was investigated. Finally, experiments were carried out to validate its performance in detection of various defects. Results indicated that even for a 1 mm through-thickness hole 700 mm away, the proposed phased array system can still detect it accurately, which is much better than previous SHM systems. Dual defects including a crack and a hole can also be clearly detected without baseline. The high-sensitivity of the proposed system was attributed to the employed bidirectional transducer which can generate non-dispersive SH0 Wave with high energy concentration. This proposed SH Wave phased array system will provide a high-performance SHM method for plate-like structures.
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A unidirectional SH Wave transducer based on phase-controlled antiparallel thickness-SHear (d15) piezoelectric strips
Theoretical and Applied Mechanics Letters, 2020Co-Authors: Mingtong Chen, Qiang HuanAbstract:Abstract In recent years, SHear horizontal (SH) Waves are being paid more and more attention to in structural health monitoring as it has only one displacement component. In this paper, a unidirectional SH Wave transducer based on phase-controlled antiparallel thickness-SHear (d15) piezoelectric strips (APS) is proposed. Here two pairs of identical APS were used each of which is a bidirectional SH Wave transducer. By setting the interval between the two pairs of APS as 1/4 Wavelength and the excitation delay between them as 1/4 period of the central operating frequency, unidirectional SH Waves can be excited. Both finite element simulations and experiments were performed to validate the proposed design. Results SHow that SH0 Waves were successfully excited only along one direction and those along the unwanted directions were suppressed very well. The proposed unidirectional SH Wave transducer is very helpful to study the fundamentals and applications of SH Waves.
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a high resolution structural health monitoring system based on SH Wave piezoelectric transducers phased array
Ultrasonics, 2019Co-Authors: Qiang Huan, Mingtong ChenAbstract:Abstract Guided Wave based structural health monitoring (SHM) has been regarded as an effective tool to detect the early damage in large structures and thus avoid possible catastrophic failure. In recent years, Lamb Wave phased array SHM technology had been intensively investigated while the inherent multi-mode and dispersive characteristic of Lamb Waves limits its further applications. In comparison, the fundamental SHear horizontal (SH0) Wave is non-dispersive with uncoupled displacements and thus more promising for defect detection. In this work, we proposed an SH0 Wave linear phased array SHM system based on our recently proposed omni-directional SH Wave piezoelectric transducer (OSH-PT). Firstly, the working principle of the phased array system was presented and the total focusing method (TFM) was employed for imaging. Then the SH0 Wave mode generated by the OSH-PT was confirmed in a defect-free plate. Finally, experiments were carried out to examine the performances of this SHM system. Results SHowed that the proposed system can detect a through-thickness hole as small as 2 mm in diameter with the location error only about 6.3 mm. Moreover, the proposed phased array system can also detect multi-defects. Due to its low working frequency and thus low attenuation, the proposed phased array system is capable of monitoring large structures. This work will lay the foundations of SH Wave based phased array SHM.
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A tunable bidirectional SH Wave transducer based on antiparallel thickness-SHear (d15) piezoelectric strips.
Ultrasonics, 2019Co-Authors: Mingtong Chen, Qiang HuanAbstract:Abstract Guided Wave based defects inspection is very promising in the field of structural health monitoring (SHM) and nondestructive testing (NDT) due to its less dissipation and thus long distance coverage. In comparison with the widely used Lamb Waves, SHear horizontal (SH) Waves are relatively simple but less investigated probably due to the traditional notion that SH Waves were usually excited by electromagnetic acoustic transducers (EMAT). In this work, we proposed a tunable method to excite single-mode bidirectional SH Waves in plates using antiparallel thickness-SHear (d15) piezoelectric strips (APS). The proposed SH Wave driving mechanism here is similar to that by using the periodic permanent magnetics (PPM) based EMAT with the period of strips equal to half of the Wavelength. Both finite element simulations and experiments were conducted to validate this transducer in excitation of bidirectional SH Waves. Results SHow that the Lamb Waves excited by single piezoelectric strip can be suppressed very well. The radiation angle of the excited bidirectional SH Wave can be reduced by extending the strip length, increasing the driving frequency or using more strips. Moreover, the APS transducer can selectively excite SH1 Wave and suppress the SH0 Wave at 174 kHz and 273 kHz in a 10 mm-thick aluminum plate. Considering its simple structure, flexible design and low excitation energy, the APS SH Wave transducer is expected to be widely used in near future.
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a uniform sensitivity omnidirectional SHear horizontal SH Wave transducer based on a thickness poled thickness SHear d15 piezoelectric ring
Smart Materials and Structures, 2017Co-Authors: Qiang Huan, Hongchen MiaoAbstract:The fundamental SHear horizontal (SH0) Wave in plates is of great importance in the field of nondestructive testing (NDT) and structural health monitoring (SHM) since it is the unique non-dispersive guided Wave mode. For practical applications, a phased array system based on omnidirectional SH0 Wave transducers is most useful as it can cover a wide range of a plate. However, so far very few omnidirectional SH Wave transducers have been developed. In this work, we proposed an omnidirectional SH Wave piezoelectric transducer (OSH-PT) based on a thickness poled piezoelectric ring. The ring is equally divided into twelve sectors and the electric field is circumferentially applied, resulting in a new thickness-SHear (d15) mode. Finite element analysis SHows that the proposed OSH-PT can excite single-mode SH0 Wave and receive the SH0 Wave only. Experiments were then conducted to examine the performance of the proposed OSH-PT. Results indicated that it can generate and receive single-mode SH0 Wave in a wide frequency range with nearly uniform sensitivities along all directions. Considering its quite simple configuration, compact size and low cost, the proposed OSH-PT is expected to greatly promote the applications of SH Waves in the field of NDT and SHM.
Mingtong Chen - One of the best experts on this subject based on the ideXlab platform.
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a high sensitivity and long distance structural health monitoring system based on bidirectional SH Wave phased array
Ultrasonics, 2020Co-Authors: Qiang Huan, Mingtong ChenAbstract:Abstract When estimating a structural health monitoring (SHM) system, its defect sensitivity and area/distance coverage are most important factors. For commonly used guided Wave sparse array system, it usually requires a reference state as the baseline which is not available in many cases. In comparison, phased array technique typically does not need the baseline in simple structures and it had been successfully used in nondestructive testing (NDT). However, currently developed phased array systems employed omni-directional transducers routinely, where the Wave energy is distributed equally along all directions thus it is not favorable for long-distance detection. In this work, bidirectional piezoelectric transducers were used to form a linear phased array system, which can generate/receive SHear horizontal (SH) Wave with high energy concentration. Firstly, the configuration of the employed transducer composed by antiparallel d15 piezoelectric strips (APS) was presented. Then the total focusing method (TFM) employed for defect detection was introduced. After validating the radiation pattern of SH Wave generated by the APS, the properties of beam steering for the proposed phased array was investigated. Finally, experiments were carried out to validate its performance in detection of various defects. Results indicated that even for a 1 mm through-thickness hole 700 mm away, the proposed phased array system can still detect it accurately, which is much better than previous SHM systems. Dual defects including a crack and a hole can also be clearly detected without baseline. The high-sensitivity of the proposed system was attributed to the employed bidirectional transducer which can generate non-dispersive SH0 Wave with high energy concentration. This proposed SH Wave phased array system will provide a high-performance SHM method for plate-like structures.
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A unidirectional SH Wave transducer based on phase-controlled antiparallel thickness-SHear (d15) piezoelectric strips
Theoretical and Applied Mechanics Letters, 2020Co-Authors: Mingtong Chen, Qiang HuanAbstract:Abstract In recent years, SHear horizontal (SH) Waves are being paid more and more attention to in structural health monitoring as it has only one displacement component. In this paper, a unidirectional SH Wave transducer based on phase-controlled antiparallel thickness-SHear (d15) piezoelectric strips (APS) is proposed. Here two pairs of identical APS were used each of which is a bidirectional SH Wave transducer. By setting the interval between the two pairs of APS as 1/4 Wavelength and the excitation delay between them as 1/4 period of the central operating frequency, unidirectional SH Waves can be excited. Both finite element simulations and experiments were performed to validate the proposed design. Results SHow that SH0 Waves were successfully excited only along one direction and those along the unwanted directions were suppressed very well. The proposed unidirectional SH Wave transducer is very helpful to study the fundamentals and applications of SH Waves.
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a high resolution structural health monitoring system based on SH Wave piezoelectric transducers phased array
Ultrasonics, 2019Co-Authors: Qiang Huan, Mingtong ChenAbstract:Abstract Guided Wave based structural health monitoring (SHM) has been regarded as an effective tool to detect the early damage in large structures and thus avoid possible catastrophic failure. In recent years, Lamb Wave phased array SHM technology had been intensively investigated while the inherent multi-mode and dispersive characteristic of Lamb Waves limits its further applications. In comparison, the fundamental SHear horizontal (SH0) Wave is non-dispersive with uncoupled displacements and thus more promising for defect detection. In this work, we proposed an SH0 Wave linear phased array SHM system based on our recently proposed omni-directional SH Wave piezoelectric transducer (OSH-PT). Firstly, the working principle of the phased array system was presented and the total focusing method (TFM) was employed for imaging. Then the SH0 Wave mode generated by the OSH-PT was confirmed in a defect-free plate. Finally, experiments were carried out to examine the performances of this SHM system. Results SHowed that the proposed system can detect a through-thickness hole as small as 2 mm in diameter with the location error only about 6.3 mm. Moreover, the proposed phased array system can also detect multi-defects. Due to its low working frequency and thus low attenuation, the proposed phased array system is capable of monitoring large structures. This work will lay the foundations of SH Wave based phased array SHM.
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A tunable bidirectional SH Wave transducer based on antiparallel thickness-SHear (d15) piezoelectric strips.
Ultrasonics, 2019Co-Authors: Mingtong Chen, Qiang HuanAbstract:Abstract Guided Wave based defects inspection is very promising in the field of structural health monitoring (SHM) and nondestructive testing (NDT) due to its less dissipation and thus long distance coverage. In comparison with the widely used Lamb Waves, SHear horizontal (SH) Waves are relatively simple but less investigated probably due to the traditional notion that SH Waves were usually excited by electromagnetic acoustic transducers (EMAT). In this work, we proposed a tunable method to excite single-mode bidirectional SH Waves in plates using antiparallel thickness-SHear (d15) piezoelectric strips (APS). The proposed SH Wave driving mechanism here is similar to that by using the periodic permanent magnetics (PPM) based EMAT with the period of strips equal to half of the Wavelength. Both finite element simulations and experiments were conducted to validate this transducer in excitation of bidirectional SH Waves. Results SHow that the Lamb Waves excited by single piezoelectric strip can be suppressed very well. The radiation angle of the excited bidirectional SH Wave can be reduced by extending the strip length, increasing the driving frequency or using more strips. Moreover, the APS transducer can selectively excite SH1 Wave and suppress the SH0 Wave at 174 kHz and 273 kHz in a 10 mm-thick aluminum plate. Considering its simple structure, flexible design and low excitation energy, the APS SH Wave transducer is expected to be widely used in near future.
Hongchen Miao - One of the best experts on this subject based on the ideXlab platform.
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a uniform sensitivity omnidirectional SHear horizontal SH Wave transducer based on a thickness poled thickness SHear d15 piezoelectric ring
Smart Materials and Structures, 2017Co-Authors: Qiang Huan, Hongchen MiaoAbstract:The fundamental SHear horizontal (SH0) Wave in plates is of great importance in the field of nondestructive testing (NDT) and structural health monitoring (SHM) since it is the unique non-dispersive guided Wave mode. For practical applications, a phased array system based on omnidirectional SH0 Wave transducers is most useful as it can cover a wide range of a plate. However, so far very few omnidirectional SH Wave transducers have been developed. In this work, we proposed an omnidirectional SH Wave piezoelectric transducer (OSH-PT) based on a thickness poled piezoelectric ring. The ring is equally divided into twelve sectors and the electric field is circumferentially applied, resulting in a new thickness-SHear (d15) mode. Finite element analysis SHows that the proposed OSH-PT can excite single-mode SH0 Wave and receive the SH0 Wave only. Experiments were then conducted to examine the performance of the proposed OSH-PT. Results indicated that it can generate and receive single-mode SH0 Wave in a wide frequency range with nearly uniform sensitivities along all directions. Considering its quite simple configuration, compact size and low cost, the proposed OSH-PT is expected to greatly promote the applications of SH Waves in the field of NDT and SHM.
Jianghai Xia - One of the best experts on this subject based on the ideXlab platform.
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Joint inversion of Love-Wave dispersion curves and SH-Wave firstarrivals for near-surface SH-Wave velocity
Proceedings of the 7th International Conference on Environment and Engineering Geophysics & Summit Forum of Chinese Academy of Engineering on Engineer, 2016Co-Authors: Xiaohan Hao, Jianghai XiaAbstract:Tomography and surface-Wave analysis are two establiSHed methods in seismic surveys and used successfully in near surface. Data acquisition, processing, and inversion of those two methods have been studied widely. Those two methods possess some different particular advantages respectively. We implemented the joint inversion of Love-Wave dispersion curves and SH-Wave first arrivals using a damped least-squares algorithm to obtain subsurface SH-Wave velocity models. The joint inversion method is tested with two synthetic seismic records. We compared results of those two individual inversion methods with those of the joint inversion method. The results indicate that we could use the joint inversion method to achieve a better real SH-Wave velocity model because the joint inversion uses more data for SH-Wave velocities in inversion. The results also indicate SH-Wave velocities of low velocity layers could also be determined using the joint inversion method.
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Finite-difference modeling of SH-Wave conversions in SHallow SHear-Wave refraction surveying
Journal of Applied Geophysics, 2015Co-Authors: Jianghai XiaAbstract:Abstract The SHallow SHear-Wave refraction method works successfully in an area with a series of horizontal layers. Complex near-surface geology, however, may not fit into the assumption of a series of horizontal layers. It is theoretically inevitable that a plane SH-Wave undergoes Wave-type conversions along an interface in an area of non-horizontal layers. One real example has SHown that the SHallow SH-Wave refraction method provides velocities of a converted Wave rather than SH-Wave. Moreover, it is impossible to identify the converted Wave by refraction data itself. In this paper, we implement numerical simulation for conversion of SH- to P-Wave in 3D heterogeneous medium with the finite-difference method. An SH-Wave source excitation method that we give in the numerical simulation is testified, which can only generate SH-Wave without P-Wave. The numerical modeling results demonstrate that the conversion of the SH-Wave to other Wave-types will occur in an area of non-horizontal layers. All the converted P-Wave arrivals are SHown reversed polarity like S-Wave arrivals in the modeling of reverse of the source and we have clarified the peculiar properties of converted P-Waves from the S-Wave. Our numerical simulation results confirm that velocities calculated from an SH-Wave refraction survey are velocities of converted Waves. Therefore, special attention SHould be paid to this pitfall in the real world.
Mikhail V. Golub - One of the best experts on this subject based on the ideXlab platform.
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Elastic SH Wave propagation in a layered anisotropic plate with interface damage modelled by spring boundary conditions
Quarterly Journal of Mechanics and Applied Mathematics, 2008Co-Authors: Anders E Boström, Mikhail V. GolubAbstract:Elastic SH Wave propagation in a layered anisotropic plate with interface damage is modelled in several steps. A single interface crack between two half-spaces is first studied and an explicit solution for the crack-opening displacement is obtained at low frequencies. This is then generalized to a random distribution of cracks at the interface and the result is reformulated as a spring boundary condition. As an example of its usefulness, this boundary condition is then used in the derivation of a plate equation by expanding the displacements in power series in the thickness coordinate.
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Elastic SH Wave propagation in a layered anisotropic plate with interface damage modelled by spring boundary conditions
Quarterly Journal of Mechanics and Applied Mathematics, 2008Co-Authors: Anders E Boström, Mikhail V. GolubAbstract:Elastic SH Wave propagation in a layered anisotropic plate with interface damage is modelled in several steps. A single interface crack between two half-spaces is first studied and an explicit solution for the crack-opening displacement is obtained at low frequencies. This is then generalized to a random distribution of cracks at the interface and the result is reformulated as a spring boundary condition. As an example of its usefulness, this boundary condition is then used in the derivation of a plate equation by expanding the displacements in power series in the thickness coordinate.
